The present invention relates to portable device navigation/positioning methods and apparatus. More specifically, embodiments of the present invention relate to methods for using global positioning system data, physical-based inertial data, and or wireless signals for navigation/positioning purposes.
One source of outdoor location geographically referenced positioning data includes Global Navigation Satellite System (GNSS). In the US, the Global Positioning System (GPS) is the most widely used standard for GNSS performance. In the present disclosure, reference to a “GPS” refers more generally to any GNSS positioning source.
The inventors recognize that conventional hand held devices rely only upon GPS signals to determine the user position, however such data is typically only available if the user has an unobstructed view of the sky. The GPS user positioning data will become significantly degraded in performance or absent altogether when the user is in the shadow of a building, inside a car park, in a subway or tunnel, transmission tower, or other types of structures or GPS interference.
Upon entry to a building, the inventors expect GPS signals to be generally unusable, and even hand-held devices including modern high-sensitivity receivers will experience spotty coverage and large uncertainty in positioning. For navigation purposes, the inventors believe that once a GPS signal is lost, it is not practical or possible to “go back” or revert to the most recent navigation solution and coast forward in time. Instead, when GPS signals are subsequently received, new navigation solutions to a destination need to be determined.
Accordingly, in various embodiments, the inventors believe that for navigation purposes, it is useful to know in advance whether GPS is about to be lost so that other navigation methods (e.g. dead reckoning) may be initiated.